The prior art envisages the use of hermetic manual pumps which are associated with containers inside which a fluid substance is present. Operation of the pump results in the dispensing of the fluid.
In pumps of the hermetic type, the amount of fluid dispensed is not replaced by air coming into the container from which the fluid is dispensed. Therefore, the container usually features a deformable bag which deforms as a consequence of the dispensing of the fluid via the pump. Instead of the deformable bag, a movable container base may be envisaged.
One drawback of these types of devices relates to the use of a flat annular gasket, which is usually interposed between the neck of the container (at the head) and a pump flange.
More specifically, with the use of conventional gaskets, it proves difficult to obtain a constant seal over time, especially when the said seal must be maintained even in depressurised conditions resulting from the partial emptying of the bag containing the fluid substance.
The various factors that negatively influence the possibility of obtaining a constant seal include the non-flatness of the mouth of the vial, especially in the event that the vial or container is made of plastic.
Another factor which negatively influences the seal is the ‘memory’ effect of the gasket, which is particularly accentuated when the inside of the container is subjected to inconstant depressurisation.
Last but not least, it proves complex, and sometimes impossible, to obtain a constant seal over time in the event of a snap (and therefore not threaded) coupling between the pump and the container. In this event, it proves difficult to adjust the pre-load on the gasket (which is obtained more easily, meanwhile, with a threaded coupling).
WO 01/26822-A1 describe a seal configured for non-hermetic pumps. The seal performed is not an air-tight seal and only works when the seal itself undergoes a deformation induced by the position of the pump.
Also, the seal described in EP 2 153 908-A1 works only in ‘deformed’ conditions. Furthermore, the seal of the cited reference, works only to prevent air to enter the container, and allows fluid to leak from the container, when the pump is fitted on it.
DE 20 2005 014895-U1 also describe a seal known in the art.